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Determine whether unilateral low-intensity blood-flow restricted (LIBFR) exercise is as effective as high-intensity (HI) resistance training for improving contralateral muscle strength. Thirty healthy adults (20–30 years) were randomly allocated to the following dynamic plantar-flexion training interventions: HI [75% of one-repetition maximum (1RM), 4 sets, 10 reps] and LIBFR [20% of 1RM, 4 sets, 30 + 15 + 15 + 15 reps]. Evoked V-wave and H-reflex recruitment curves, as well as maximal voluntary contraction (MVC) and panoramic ultrasound assessments of the trained and untrained soleus muscles were obtained pre-training, post-4 weeks of training and post-4 weeks of detraining. Both interventions failed to increase contralateral MVC and muscle cross-sectional area (CSA). Yet, contralateral rate of torque development (RTD) was enhanced by both regimens (12–26%) and this was accompanied by heightened soleus EMG within the first milliseconds of the rising torque-time curve (14–22%; p

Purpose: This study aimed (1) to analyze the interindividual variability in the maximal number of repetitions (MNR) performed against a given relative load (percentage of 1-repetition maximum [%1RM]) and (2) to examine the relationship between the velocity loss (VL) magnitude and the percentage of completed repetitions with regard to the MNR (%Rep), when the %1RM is based on individual load–velocity relationships. Methods: Following an assessment of 1RM strength and individual load–velocity relationships, 14 resistance-trained men completed 5 MNR tests against loads of 50%, 60%, 70%, 80%, and 90% 1RM in the Smith machine bench-press exercise. The relative loads were determined from the individual load–velocity relationship. Results: Individual relationships between load and velocity displayed coefficients of determination (R2) ranging from .986 to .998. The MNR showed an interindividual coefficient of variation ranging from 8.6% to 33.1%, increasing as the %1RM increased. The relationship between %Rep and the magnitude of VL showed a general R2 of .92 to .94 between 50% and 80% 1RM, which decreased to .80 for 90% 1RM. The mean individual R2 values were between .97 and .99 for all loading conditions. The %Rep when a given percentage of VL was reached showed interindividual coefficient of variation values ranging from 5% to 20%, decreasing as the %Rep increased in each load condition. Conclusions: Setting a number of repetitions had acceptable interindividual variability, with moderate relative loads being adjusted based on the individual load–velocity relationship. However, to provide a more homogeneous level of effort between athletes, the VL approach should be considered, mainly when using individual VL–%Rep relationships.

Background: An increasing body of evidence indicates that the phase angle (PhA) can be applied as a marker of nutritional status, disease prognosis, and mortality probability. Still, it is not known whether PhA can be used as an indicator of muscular quantity and strength and maximal aerobic capacity in overweight/obese former highly active individuals, an understudied population. This study aimed to analyze the association between PhA with skeletal muscle mass, maximal isometric strength, and maximal aerobic capacity through VO2max, in overweight/obese and inactive former athletes. Methods: Cross-sectional information of 94 (62 males) former adult athletes (age: 43.1 ± 9.4 years old; body mass index: 31.4 ± 4.8 kg/m2) taking part in a weight-loss clinical trial was analyzed. Total fat and fat-free mass were determined by dual-energy X-ray absorptiometry, while skeletal muscle mass was predicted from appendicular lean soft tissue. Values for upper- and lower-body maximal isometric strength were assessed by handgrip and leg press dynamometry. VO2max was determined by indirect calorimetry through a graded exercise test performed on a treadmill. Results: PhA was associated with skeletal muscle mass (r = 0.564, p < 0.001), upper-body strength (r = 0.556, p < 0.001), lower-body strength (r = 0.422, p < 0.001), and VO2max (r = 0.328, p = 0.013). These relationships remained significant for skeletal muscle mass (β = 2.158, p = 0.001), maximal isometric strength (upper-body: β = 2.846, p = 0.012; low-er-body: β = 24.209, p = 0.041) after adjusting for age, sex, and fat mass but not for VO2max (β = −0.163, p = 0.098). Conclusion: Our findings indicated that former athletes with higher values of PhA exhibited greater muscle mass and strength, despite sex, age, and body composition, which suggests that this simple raw BI parameter can be utilized as an indicator of muscle quantity and functionality in overweight/obese former athletes.

Gonçalves, BM, Mesquita, RNO, Tavares, F, Brito, J, Correia, P, Santos, P, and Mil-Homens, P. A new portable device to reliably measure maximal strength and rate of force development of hip adduction and abduction. J Strength Cond Res 36(9): 2465-2471, 2022-Groin injuries are a major issue in sports involving kicking or quick changes of direction. Decreased hip adduction and abduction strength have been indicated as one of the main risk factors for groin injury. The methods currently available to measure hip adduction and abduction strength are reliable but highly dependent on the evaluator skills. Furthermore, several studies have reported the reliability of maximal strength (MVIC), but very few studies investigated the reliability of explosive strength (RFD), a parameter that has been previously shown to have a higher functional value. The aim of the current investigation was to assess the reliability of a user-independent portable dynamometer that concurrently measures MVIC and RFD. Twenty-five healthy young subjects performed maximal isometric hip adduction and abduction in both sitting and supine positions. Measurements occurred in 2 different days separated by 48-72 hours. Test-retest reliability was calculated for both MVIC and RFD. Both MVIC and RFD showed good relative reliability (intraclass correlation coefficient = 0.77-0.98) with no differences between positions or muscle actions. Measurement error was similar between positions for MVIC in both hip adduction and abduction. Measurements of RFD showed higher reliability using a time window of at least 0-100 milliseconds, and lower measurement error was observed in sitting for adduction and in supine for abduction. This study shows that portable dynamometry can be used to concurrently measure hip adduction and abduction maximal and explosive strength, with levels of reliability that are similar to previously described methods.

Riscart-Lopez, J, Rendeiro-Pinho, G, Mil-Homens, P, Costa, RS-d, Loturco, I, Pareja-Blanco, F, and Leon-Prados, JA. Effects of Four different velocity-based training programming models on strength gains and physical performance. J Strength Cond Res 35(3): 596-603, 2021-The aim of this study was to compare the effects of 4 velocity-based training (VBT) programming models (linear programming [LP], undulating programming [UP], reverse programming [RP], and constant programming [CP]) on the physical performance of moderately strength-trained men. Forty-three young (age: 22.9 ± 4.8 years; body mass [BM]: 71.7 ± 7.6; full squat [SQ] relative strength 1.32 ± 0.29) subjects were randomly assigned to LP (gradually increase training intensity and decrease volume), UP (volume and intensity increase or decrease repeatedly), RP (gradually increases volume and decrease intensity), and CP (maintains constant volume and intensity) groups and followed an 8-week VBT intervention using the SQ exercise and monitoring movement velocity for every repetition. All groups trained with similar relative average intensity (67.5% 1 repetition maximum [1RM]), magnitude of velocity loss within the set (20%), number of sets (3), and interset recoveries (4 minutes) throughout the training program. Pre-training and post-training measurements included predicted SQ (1RM), average velocity attained for all loads common to pre-tests and post-tests (AV), average velocity for those loads that were moved faster (AV > 1) and slower (AV < 1) than 1 m·s-1 at pre-tests, countermovement jump height (CMJ), and 20-m sprint time (T20). No significant group × time interactions were observed for any of the variables analyzed. All groups obtained similar increases (shown in effect size values) in 1RM strength (LP: 0.88; UP: 0.54; RP: 0.62; CP: 0.51), velocity-load-related variables (LP: 0.74-4.15; UP: 0.46-5.04; RP: 0.36-3.71; CP: 0.74-3.23), CMJ height (LP: 0.35; UP: 0.53; RP: 0.49; CP: 0.34), and sprint performance (LP: 0.34; UP: 0.35; RP: 0.32; CP: 0.30). These results suggest that different VBT programming models induced similar physical performance gains in moderately strength-trained subjects.

Ultrasound imaging allows the evaluation of musculoskeletal morphology and function. Ultrasound elastography can also offer semi-quantitative and/or quantitative assessment of tissue stiffness providing relevant information about adaptations of skeletal muscle mechanical properties. In this study we aimed to explore the feasibility of elastography ultrasound imaging in assessing the effect of strength training on vastus lateralis stiffness. Twenty-eight young male adults were separated in a control (n = 9) and strength-training (n = 20) groups. The strength-training group completed 15 weeks of either concentric (n = 10) or eccentric (n = 10) isokinetic training of the knee extensors. Ultrasound scans of the vastus lateralis for quasi-static elastography were collected. All image acquisitions and measurements were done by the same experienced sonographer. After 15 weeks, knee maximal extension isometric torque increased in the strength-training groups. After strength training, there was a decrease in the amount of red pixels in vastus lateralis region of interest [F(1,18) = 25.490, p &lt, 0.001, &eta, 2 = 0.586], whereas the amount of green and blue pixels increased F(1,18) = 17.179, 0.01, 2 = 0.488, F(1,18) = 6.522, 0.05, 2 = 0.266], suggesting higher vastus lateralis stiffness. We conclude that concentric and eccentric strength training increases skeletal muscle stiffness, which can be evaluated by quasi-static elastography. Ultrasound elastography is suitable for non-invasive evaluation of skeletal muscle functional adaptations, which can be of importance for sports medicine and in designing optimal training and rehabilitation programs.

This study aimed to determine whether men and women display a different magnitude of muscle fatigue in response to high-load (HL) and low-load blood flow-restricted (LLBFR) elbow-flexion exercise. We also explored to which extent both exercise protocols induce similar levels of muscle fatigue (i.e., torque decrement). Sixty-two young participants (31 men and 31 women) performed dynamic elbow flexions at 20 and 75% of one-repetition maximum for LLBFR and HL exercise, respectively. Maximum voluntary isometric contractions were performed before and after exercise to quantify muscle fatigue. Men and women exhibited similar magnitude of relative torque decrement after both exercise protocols (p > 0.05). HL was more fatiguing (∆ torque output: 11.9 and 23 N.m in women and men, respectively) than LLBFR resistance exercise (∆ torque output: 8.3 and 15.4 N.m in women and men, respectively) in both sexes, but this was largely attenuated after controlling for the differences in volume load between protocols (p > 0.05). These data show that torque decrement in response to LLBFR and HL dynamic elbow-flexion exercise does not follow a sexually dimorphic pattern. Our data also indicate that, if performed in a multiple-set fashion and prescribed for a given volume load, elbow-flexion LLBFR exercise induces similar levels of fatigue as HL acute training. Importantly, this occurs similarly in both sexes.

Fatela, P, Reis, JF, Mendonca, GV, Freitas, T, Valamatos, MJ, Avela, J, and Mil-Homens, P. Acute neuromuscular adaptations in response to low-intensity blood flow restricted exercise and high-intensity resistance exercise: are there any differences? J Strength Cond Res 32(4): 902-910, 2018-Numerous studies have reported similar neuromuscular adaptations between low-intensity (LI) blood-flow restricted exercise (BFRE) and high-intensity (HI) resistance training. Unfortunately, none of these experimental designs individualized blood flow restriction (BFR) levels to each participant. Thus, their findings are difficult to interpret. We aimed at comparing the acute effects of LI BFR (80% of absolute vascular occlusion pressure) with LI non-BFR and HI training on muscle torque, activation, and neuromuscular fatigue. Ten men (23.8 ± 5.4 years) exercised at 20 and 75% of 1 repetition maximum with and without BFR (for LI). Blood flow restriction pressure was determined individually using resting blood-flow measurements. Torque was determined during maximal voluntary contractions (MVCs) at pre-exercise and postexercise time points. Surface electromyographic activity (root mean square [RMS] and median frequency [MF]) was recorded for the rectus femoris (RF) and vastus medialis (VM) muscles, before and after each session of training, during isometric contractions at 20% MVC. Torque decreased post-HI and LI BFR (-9.5 and -7.8%, respectively; p < 0.01), but not after LI non-BFR. The MF was reduced following HI training in the VM and the RF muscles (-5.3 and -12.5%, respectively; p ≤ 0.05). Conversely, the impact of LI BFR on reducing MF was limited to the RF muscle (-10.7%, p ≤ 0.05). Finally, when compared to all other conditions, RMS values were consistently higher during submaximal contractions performed after HI training (p ≤ 0.05). Thus, we conclude that, despite enhancing the acute magnitude of muscular activation and fatigue, LI BFR exercise exerts a less profound impact on neuromuscular function than HI resistance training.

Objectives Biceps femoris long-head architectural assessment using ultrasonography (US) has not been previously described in detail for both acquisition (image capture) and digitization (image measurement) processes, and the effect of the US window width is unknown. This study aimed to describe the reliability and test-retest minimum detectable difference of US-based biceps femoris architectural measurements. Methods Muscle length was determined by marking the muscle-tendon junction distances. Sonograms were acquired with a 6-cm image width and cropped for a 3-cm width in 3 assessments (n = 20 adults). Intra- and inter-rater reliability rates were determined for both image (3- and 6-cm widths) acquisition and digitizing processes separated and together (within session) for the biceps femoris fascicle length, fascicle angle, and muscle thickness measurements using intraclass correlation coefficients (ICCs) and Pearson (r) correlation coefficients. Results Muscle length was measured with high intra-rater (ICC = 0.93; r = 0.92) and inter-rater (ICC = 0.90; r = 0.90) reliability. Intra-rater (coefficient of variation, 0.2%–1.8%) and inter-rater (ICC = 0.79–0.99; r = 0.80–0.99) digitizing reliability rates were high. High intra-rater (ICC = 0.79–0.95; r = 0.79–0.95) and moderate-to-high inter-rater (ICC = 0.51–0.92; r = 0.70–0.93) session reliability rates were found for all architectural parameters for 6- and 3-cm images (intra-rater ICC = 0.77–0.93; r = 0.79–0.93; inter-rater ICC = 0.63–0.98; r = 0.90–0.98). The inter-rater session reliability rates for both image acquisition and digitizing processes were higher for 6-cm images (ICC = 0.65–0.86; r = 0.67–0.87) than 3-cm images (ICC = 0.28–0.93; r = 0.67–0.93). The minimum detectable differences for the 6-cm images were 8.4 mm, 1.5 °, and 1.6 mm for fascicle length, fascicle angle, and muscle thickness, respectively. Conclusions Ultrasonography can be used to reliably assess midmuscle architecture of the biceps femoris muscle when the same rater performs image acquisition and digitization.

Hamstring strain injuries (HSI) are the most common injury in male professional football and are potentially a primary risk factor to re-injury. Although the isokinetic strength ratios have often been used to identify strength imbalances that can augment the risk of injury in football players, the rate of torque development hamstring to quadriceps ratio (RTD H/Q) has rarely been considered in previous reports. Furthermore, little consideration has been given to selective hamstring lengths (30° of knee flexion) and its influence on torque production. The aim of this study was to investigate the RTD H/Q at long hamstring lengths, conventional (concentric/concentric) and functional (eccentric/concentric) H/Q ratios in football players with and without previous HSI. Twenty-four professional male football players (12 and 12 without previous HSI) performed maximal voluntary isometric contractions at long hamstring lengths (knee and hip flexed at 30° and 85°, respectively) and isokinetic concentric and eccentric contractions at 180°.s

We aimed to determine whether blood flow restriction (BFR) alters the characteristics of individual motor units during low-intensity (LI) exercise. Eight men (26.0±3.8 yrs) performed 5 sets of 15 knee extensions at 20% of one-repetition maximum (with and without BFR). Maximal isometric voluntary contractions (MVC) were performed before and after exercise to quantify force decrement. Submaximal isometric voluntary contractions were additionally performed for 18 s, matching trapezoidal target-force trajectories at 40% pre-MVC. EMG activity was recorded from the vastus lateralis muscle. Then, signals were decomposed to extract motor unit recruitment threshold, firing rates and action potential amplitudes (MUAP). Force decrement was only seen after LI BFR exercise (–20.5%; p

The objective of this investigation was to evaluate the accuracy of peak vertical jump power (VJP) to identify children with bone mineral density (BMD) below average, defined as BMD measured by DXA and adjusted for body height at the whole body less head≤- 1.0 standard deviation (SD). The sample included 114 boys and girls aged 8.5±0.4 years old. VJP was estimated from a countermovement jump performed on a contact mat using the measured flight time to calculate the height of rise of the center of gravity. Logistic regression analysis revealed that the odds ratio of having BMD≤1.0 SD decreased 1.2% per watt of power and the probability of BMD below average was 75.6% higher in boys than in girls with the same peak power jump. Receiver operating characteristic analysis showed that the best trade-off between sensitivity and specificity to identify children with BMD- 1.0 SD was 635 watts in boys (sensitivity=63.3%; specificity=69.2%; AUC=0.816, 95% CI: 0.681-0.95; p0.001) and 515 watts in girls (sensitivity=75.0%; specificity=77.0%; AUC=0.849, 95% CI: 0.698-0.999; p=0.002). These cut-off values correspond to a vertical jump of 19.9 cm and 20.5 cm in 8-year-old boys and girls, respectively. The VJP showed a reasonable sensitivity and specificity as well good discriminant ability to identify children with BMD below average.

There is some evidence that muscular activation during exercise is enhanced by higher levels of blood flow restriction (BFR). However, the impact of different relative levels of BFR on the acute neuromuscular response to resistance exercise is not yet fully understood. We examined the acute effects of low-intensity knee extensions [20 % of 1-repetition maximum (1RM)] with BFR on muscle activation, neuromuscular fatigue and torque in the rectus femoris (RF) and vastus medialis (VM) muscles. Fourteen men (24.8 ± 5.4 years) exercised at 20 % 1RM combined with 40, 60 and 80 % BFR. Restrictive pressures were calculated based on direct blood-flow measurements taken at rest on each participant. Torque was determined during pre- and post-exercise maximal voluntary contractions. Surface electromyographic activity [root mean square (RMS)] was obtained during dynamic and sustained isometric contractions before and after exercise. The median frequency (MF) of the electromyographic power spectrum was computed for isometric contractions. Torque only decreased in the 80 % BFR condition (−5.2 %; p

PURPOSE The V wave is an electrophysiologic variant of the H reflex that is evoked with supramaximal stimulus intensity. In this study, we explored whether the between-day reliability of V-wave normalized amplitude varies as a function of the number of intrasession measurement trials. We also determined whether the reliability of the V wave improves after the exclusion of the initial testing trials. METHODS Eighteen healthy, young participants (10 men and 8 women) were included in this study. Test-retest reliability was assessed using intraclass correlation coefficients and the standard error of the measurement (1.96*SEM). RESULTS The intraclass correlation coefficient values of the V-wave normalized amplitude increased in a progressive fashion with the inclusion of more than two measurement trials (from 0.41 to 0.75). The 1.96*SEM scores also decreased from 12.47% to 7.60% after calculating the V-wave normalized amplitude from five versus two measurement trials. After excluding the first two trials from V-wave calculations, the intraclass correlation coefficient and the 1.96*SEM score attained values of 0.88 and 6.54%, respectively. CONCLUSIONS Our findings indicate that the test-retest reliability of the V-wave response increases in a progressive fashion with more than two intrasession measurement trials (up to five trials). It also shows that to ensure maximal reliability, the first two measurement trials should be discarded from V-wave computations.

Borges, A, Teodósio, C, Matos, P, Mil-Homens, P, Pezarat-Correia, P, Fahs, C, and Mendonca, GV. Sexual dimorphism in the estimation of upper-limb blood flow restriction in the seated position. J Strength Cond Res 32(7): 2096-2102, 2018-Arterial occlusion pressure (AOP) is typically used to normalize blood flow restriction (BFR) during low-intensity BFR exercise. Despite strong evidence for sexual dimorphism in muscle blood flow, sex-related differences in AOP estimation remain a controversial topic. We aimed at determining whether the relationship of upper-limb AOP with arm circumference and systolic blood pressure (BP) differs between men and women resting in the seated position. Sixty-two healthy young participants (31 men: 21.7 ± 2.3; 31 women: 22.0 ± 2.0 years) were included in this study. Arm circumference, resting BP, and AOP were taken in the seated position. Multiple linear regression analysis was used to determine whether the relationship of AOP with arm circumference and resting BP differed between sexes. Prediction accuracy was assessed with the mean absolute percent error and Bland-Altman plots. Men had higher systolic BP and larger arm circumference than women (p0.05). Nevertheless, AOP was similar between sexes. Arm circumference, systolic BP, and sex were all significant predictors of AOP (p0.05), explaining 42% of its variance. The absolute percent error was similar in both sexes (men: -0.55 ± 7.12; women: -0.39 ± 6.31%, p0.05). Bland-Altman plots showed that the mean difference between actual and estimated AOP was nearly zero in both groups, with no systematic overestimation or underestimation. In conclusion, arm circumference, systolic BP, and sex are all significant predictors of upper-limb-seated AOP. Their measurement allows for the indirect estimation of BFR pressure within the context of exercise training.

The purpose of this study was to determine the effect of a 15-week partial range of motion (ROM) resistance training program on the vastus lateralis (VL) architecture and mechanical properties, when the time under tension (TUT) was equalized. Nineteen untrained male subjects were randomly assigned to a control (Control; n = 8) or training (TG; n = 11) group. In the TG, the dominant and nondominant legs were randomly selected to be trained with a full ROM (FULL) or a partial ROM (PART) in an isokinetic dynamometer. Training volume was equalized based on the TUT by manipulating sets and repetitions. The VL muscle architecture was assessed by B-mode ultrasonography at rest and during maximal isometric knee extension contractions (MVCs) at ten knee angles. The VL fascicle force and specific tension were calculated from the MVCs with superimposed stimuli, accounting for the moment arm length, muscle architecture, and antagonist coactivation. The FULL training induced changes in fascicle length (FL) (4.9 ± 2.0%, P

Ultrasound (US) has an important role in musculoskeletal (MSK) evaluation, allowing the study of muscle morphology and function. Muscle thickness (MT) and muscle echo-intensity (EI) are two important parameters that may quantify muscle structural adaptations to a variety of stimuli. The aim was to explore the potential of quantitative US imaging for assessing the adaptations and responses of the muscle tissue to increased contractile activity using B-mode US. This study was centred on the quadriceps femoris muscle contractile activity on MT and EI.Twenty-eight young male adults participated in the study, divided in a control group and two training groups performing concentric or eccentric strength training, respectively. The effect of a 15-week strength program was studied on MT and EI in several regions of the heads of the quadriceps femoris using B-mode US. All images acquisitions and measurements were done by the same experience sonographer.Strength training resulted in an increase of MT at all muscles and sites (p 0.05), except the VM. Strength training failed in changing EI in most of the quadriceps femoris, except in the VI and some regions of the VL. No statistically significant differences were observed in our quantitative US parameters between concentric and eccentric training (p 0.05).These results emphasise the value of MT as a quantifiable muscle US method for evaluating muscle adaptation to exercise training. However, the inconsistency of the EI values indicates that more studies are needed to develop it as an accurate diagnostic tool.

Static stretching with rest between repetitions is often performed to acutely increase joint flexibility.Purpose:To test the effects of the lack of resting between stretching repetitions and the minimal number of stretching repetitions required to change the maximal range of motion (ROM), maximal tolerated joint passive torque (MPT), and submaximal passive torque at a given angle (PT).Methods:Five static stretching repetitions with a 30-s rest-interval (RI) and a no-rest-interval (NRI) stretching protocol were compared. Participants (N = 47) were encouraged to perform the maximal ROM without pain in all the repetitions. Each repetition lasted 90 s. Maximal ROM, MPT, PT, and muscle activity were compared between protocols for the same number of stretching repetitions.Results:The NRI produced a higher increase in maximal ROM and MPT during and after stretching (P < .05). PT decreased in both protocols, although the NRI tended to have a lower decrement across different submaximal angles (.05 < P < .08) in the initial range of the torque-angle curve. Significant changes in maximal ROM (P < .01) and PT (P < .01) were obtained at the 3rd and 2nd repetitions of RI, respectively. The RI did not significantly increase the MPT (P = .12) after stretching; only the NRI did (P < .01).Conclusions:Lack of rest between repetitions more efficiently increased the maximal ROM and capacity to tolerate PT during and after stretching. The use of 30 s rest between repetitions potentiates the decrease in PT. Rest intervals should not be used if the aim is to acutely increase maximal ROM and peak passive torque.

BACKGROUND: The isokinetic hamstrings to quadriceps (H:Q) dynamic control ratio (DCR) is frequently used to assess muscle imbalances and to screen for potential risks of knee injuries in sports. OBJECTIVE: To investigate the correlation between knee conventional ratio (CR) and DCR in elite soccer players and check for a possible relationship. A positive correlation would indicate that the CR could predict DCR. METHODS: One hundred and thirteen Brazilian elite soccer players (25.2 ± 5.3 yrs) performed maximal dominant and nondominant knee concentric (CON) and eccentric (ECC) strength tests at 60◦/s on an isokinetic dynamometer in order to calculate CR and DCR. RESULTS:A significant positive correlation between ratios was found for the dominant and non-dominant knees (r = 0.54 and 0.62; p < 0.001 which translated into low R values of 0.29 and 0.39, respectively. CONCLUSION: This suggests that the CR may not replace the DCR and is thus of a limited clinical value in assessing knee muscles imbalance. On the other hand, the paper presents for the first time a robust reference frame for the isokinetic strength and related ratios of the two major knee muscles in soccer players.

International audience; PurposeWe investigated the effects of plantarflexor static stretching of different intensities on the medial gastrocnemius (GAS) shear elastic modulus, GAS fascicle length and ankle passive torque–angle responses during and after stretching.MethodsParticipants performed three stretching sessions of different intensities: 40 % (R40) of maximal dorsiflexion range of motion (ROM), 60 % (R60) of ROM, and 80 % (R80) of ROM. Each stretching lasted 10 min. The GAS architecture, GAS shear elastic modulus, ankle passive torque–angle, and muscle activity were assessed before, during, and after the stretching.ResultsThe absolute and relative (i.e., normalized to the static stretching start value) GAS shear elastic modulus relaxation varied across stretching intensities. The absolute passive torque relaxation varied across intensities (p < 0.05) but not when normalized to the stretching start value. No significant changes were observed in GAS fascicle length during the stretching (p = 0.93). After stretching, passive torque at a given angle was significantly decreased for R60 [−0.99 ± 0.59 Nm (−6.5 ± 3.8 %), p < 0.001] and R80 [−1.05 ± 1.12 Nm (−6.8 ± 6.3 %), p = 0.004], and GAS shear elastic modulus decreased only for the R80 [−9.3 ± 7.2 kPa (−14.1 %), p = 0.003]. No significant correlations were found between the magnitude of relaxation during stretching and post-stretching effect in the GAS shear elastic modulus or ankle passive torque variables. No significant relation was found between the shear elastic modulus and the ankle passive torque responses during and after stretching.ConclusionThe effects of stretching on joint passive torque do not reflect changes in the medial gastrocnemius shear elastic modulus, and these responses to stretching depend on its intensity.

Information regarding the effects of stretching intensity on the joint torque-angle response is scarce. The present study examined the effects of three static stretching protocols with different intensities and durations on the passive knee extension torque-angle response of seventeen male participants (age ± SD: 23.9 ± 3.6 years, height: 177.0 ± 7.2 cm, BMI: 22.47 ± 1.95 kg · m(2)). The stretching intensity was determined according to the maximal tolerable torque of the first repetition: fifty per cent (P50), seventy-five per cent (P75) and the maximum intensity without pain (P100). Five repetitions were performed for each protocol. The stretch duration of each repetition was 90, 135 and 180 s for P100, P75 and P50, respectively. The rest period between repetitions was 30 s. Passive torque at a given angle, angle, stress relaxation, area under the curve, surface electromyography activity and visual analogue scale score were compared. The significant (P < 0.05) results found were as follows: (i) the P50 and P75 did not increase the angle and passive peak torque outcomes, despite more time under stretch; (ii) only the P100 increased the angle and passive peak torque outcomes; (iii) the perception of stretching intensity mainly changed depending on knee angle changes, and not passive torque; (iv) the P50 induced a higher passive torque decrease; (v) when protocols were compared for the same time under stretch, the torque decrease was similar; (vi) the change in torque-angle curve shape was different depending on the stretching protocol. In conclusion, higher stretch duration seems to be a crucial factor for passive torque decrease and higher stretch intensity for maximum angle increase.

Previous studies have used isokinetic dynamometry to assess joint torques and angles during passive extension of the knee, often without reporting upon methodological errors and reliability outcomes. In addition, the reliability of the techniques used to measure passive knee extension torque-angle and the extent to which reliability may be affected by the position of the subjects is also unclear. Therefore, we conducted an analysis of the intra- and inter-session reliability of two methods of assessing passive knee extension: (A) a 2D kinematic analysis coupled to a custom-made device that enabled the direct measurement of resistance to stretch and (B) an isokinetic dynamometer used in two testing positions (with the non-tested thigh either flexed at 45° or in the neutral position). The intra-class correlation coefficients (ICCs) of torque, the slope of the torque-angle curve, and the parameters of the mathematical model that were fit to the torque-angle data for the above conditions were measured in sixteen healthy male subjects (age: 21.4 ± 2.1 yr; BMI: 22.6 ± 3.3 kg m(-2); tibial length: 37.4 ± 3.4 cm). The results found were: (1) methods A and B led to distinctly different torque-angle responses; (2) passive torque-angle relationship and stretch tolerance were influenced by the position of the non-tested thigh; and (3) ICCs obtained for torque were higher than for the slope and for the mathematical parameters that were fit to the torque-angle curve. In conclusion, the measurement method that is used and the positioning of subjects can influence the passive knee extension torque-angle outcome.

This study examined whether a high-intensity, moderate-duration bout of stretching would produce the same acute effects as a low-intensity, long-duration bout of stretching. 17 volunteers performed 2 knee-flexor stretching protocols: a high-intensity stretch (i. e., 100% of maximum tolerable passive torque) with a moderate duration (243.5 ± 69.5-s); and a low-intensity stretch (50% of tolerable passive torque) with a long duration (900-s). Passive torque at a given sub-maximal angle, peak passive torque, maximal range of motion (ROM), and muscle activity were assessed before and after each stretching protocol (at intervals of 1, 30 and 60 min). The maximal ROM and tolerable passive torque increased for all time points following the high-intensity stretching (p0.05), but not after the low-intensity protocol (p0.05). 1 min post-stretching, the passive torque decreased in both protocols, but to a greater extent in the low-intensity protocol. 30 min post-test, torque returned to baseline for the low-intensity protocol and had increased above the baseline for the high-intensity stretches. The following can be concluded: 1) High-intensity stretching increases the maximal ROM and peak passive torque compared to low-intensity stretching; 2) low-intensity, long-duration stretching is the best way to acutely decrease passive torque; and 3) high-intensity, moderate-duration stretching increases passive torque above the baseline 30 min after stretching.

This study aimed to develop a valid and reliable scale to assess the perception of stretching intensity below and above the maximal range of motion. Experiments were conducted through a passive leg extension angle-torque assessment to healthy population (n = 90). In the study's first phase, the visual, numerical, and description of the stretching intensity scale (SIS) components were developed. The visual analog scale (VAS) score, absolute magnitude estimation (AME) score, and verbal stretching intensity symptom descriptors were assessed for different stretching intensities. In the second phase, the SIS was tested for validity, reliability, scale production, and estimation properties as well as responsiveness to stretching. In the first phase, a high correlation was found between SIS score and range of motion (ROM), as well as SIS and torque in both submaximal (intraclass correlation coefficient [ICC] = 0.89-0.99, r = 0.88-0.99) and supramaximal (ICC = 0.75-0.86, r = 0.68-0.88) stretching intensities. The AME and VAS scores fitted well in an exponential model for submaximal stretching intensities (y = 14.829e, ICC = 0.97 [0.83-0.99], r = 0.98), and in a linear model for supramaximal stretching intensities (y = 0.7667x - 25.751, ICC = 0.97 [0.89-0.99], r = 0.9594). For the second phase, a high correlation was found between SIS score and ROM (r = 0.70-0.76, ICC = 0.76-0.85), as well as SIS and torque (r = 0.62-0.88, ICC = 0.57-0.85). The interday reliability was high to produce (r = 0.70, ICC = 0.70 [0.50-0.83]) or estimate (r = 0.89, ICC = 0.89 [0.82-0.93]) stretching intensities. The acute stretching effects on ROM and passive torque were detectable using the SIS. It is expected a high application in assessing the stretch intensity using the SIS in future studies and practical interventions.

Speed and distance covered during training sessions and competitions of youth soccer players.

Previous studies have reported no changes on muscle architecture (MA) after static stretching interventions; however, authors have argued that stretching duration and intensity may not have been sufficient. A high-intensity stretching intervention targeting the knee flexors with an 8-week duration was conducted to observe the effects on biceps femoris long head (BF) architecture. Participants (n = 5) performed an average of 3.1 assisted-stretching sessions per week, whereas a control group (n = 5) did not perform stretching. The knee extension passive maximal range of motion (ROM), and BF fascicle length (FL), fascicle angle, and muscle thickness were assessed before and after the intervention. A significant increase was observed for FL (+12.3 mm, p = 0.04) and maximal ROM (+14.2°, p = 0.04) for the stretching group after the intervention. No significant changes were observed for the control group in any parameter. An 8-week high-intensity stretching program was observed to efficiently increase the BF FL, as well as the knee extension maximal ROM. Stretching intensity and duration may play an important role on MA adaptation.

Objective Little is known about the influence of different training types on relative fat mobilization with exercise. The purpose of this study was to analyze the changes induced by aerobic training (AT), resistance (RT) or a combination of both (AT+RT) on total fat mass (TFM) and regional fat mass (RFM). Further, the relative contribution of different regions, upper limbs (UL), lower limbs (LL), and trunk (Tr), were compared. Design and Methods Forty-five overweight and premenopausal women were randomized in either AT, RT or AT+RT. All training groups exercised for the same duration (60 min), 3 times per week for 5 months. Body composition was estimated using dual energy X-ray absorptiometry. Results TFM decreased significantly in all groups (−4.6 ± 1.9 kg; −3.8 ± 2.6 kg, and −4.7 ± 3.0 kg in AT, RT, and AT+RT groups respectively; P < 0.001). The relative contribution of FM into each segment changed significantly: TrFM represented 46.6% ± 5.8% of TFM at baseline and reduced to 43.1% ± 5.5% (P < 0.001); LLFM was 39.7% ± 5.8% vs. 41.6% ± 5.7% (P < 0.01); ULFM was 11.3% ± 1.3% vs. 12.2% ± 1.4% (P < 0.01). Conclusion Training type did not influence changes of TFM and RFM. Fat mobilization came predominantly from Tr in all training protocols. These findings suggest that overweight and obese women can reduce TFM and RFM, independently of training type.

No âmbito deste trabalho, procuram-se discutir algumas questões sobre o processo de institucionalização de idosos e ainda refletir sobre sua influência relativamente às relações familiares, à solidão e ao isolamento social. Foram inquiridos vinte e seis idosos institucionalizados em IPSS’s nos concelhos de Coimbra e de Odemira por hetero - administração de questionários e escalas e os resultados mostram que o processo de institucionalização na valência de lar de idosos não influencia situações de solidão social verificando-se, contudo, uma diminuição da interação familiar e social em consequência daquele. Os dados mostram ainda não haver uma relação positiva entre influência negativa da institucionalização e a qualidade de vida percebida pelo idoso. / With this study I intend to discuss some questions about the process of institutionalization of old people, as well as reflect about its influence regarding family relationships, loneliness and social isolation. Twenty six IPSS institutionalized elders in the counties / municipalities of Coimbra and Odemira, were inquired by heteroadministration of questionnaires and scales. The results showed that the process of institutionalization in nursing homes does not influence situations of social loneliness, although a decrease in family and social interaction is visible as a result of the institutionalization. The data also shows that there isn’t a positive relation between the negative influence of institutionalization and the quality of life perceived by the elders.

Purpose People vary in flexibility regarding maximum joint angle, resistance to stretch and mechanical responses during stretching exercises. Body composition (BC) has been been mentioned as one of the factors for flexibility differences. The aim of this study was to determine how body composition and anthropometric measures of the lower limb is associated with passive knee extension (PKE) torque-angle (T-A) response. Methods Twenty-five male subjects with poor flexibility performed a maximal PKE repetition (velocity of 2°/s; 90 seconds in the static phase). Knee passive T-A, vastus medialis and semitendinosous electromyographic activity were recorded during the protocol. Viscoelastic stress relaxation (VSR) amplitude, knee passive stiffness (KPS), lower limb body composition assessed by dual energy x-ray absorptiometry, and anthropometry measures were determined. Results Thigh skeletal muscle and bone mass, as well as thigh perimeter, showed a moderated correlation with passive torque (r = 0.45; r = 0.6; r = 0.59, respectively), joint angle (r = 0.46; r = 0.5; r = 0.5), and VSR (r = 0.46; r = 0.49; r = 0.5). Thigh skeletal muscle was also correlated with KPS (r = 0.42). All these correlations were statistically significant (p

In the context of physical education curricula, markers of physical fitness (e.g., aerobic capacity, muscu- lar strength, flexibility, and body mass index or body fat) are usually evaluated in reference to health standards. Despite their possible mediating role in the relationship between weight-bearing or muscle forces and features of bone tissue, these attributes of fitness may not be the most relevant to predict skeletal health. It is therefore important to analyze the relative contribution of these factors to the variability in bone tissue of different parts of the skeleton, and to analyze it by gender, as sensitivity to mechanical loading can diverge for boys and girls. We compared the effects of habitual physical activity (PA) and lean mass, as surrogates of weight-bearing and muscle forces, and of physical fitness (aerobic and muscle capacity of lower and upper limbs) on bone mineral content (BMC) and size of total body, lumbar spine, femoral neck, and 1/3 radius in 53 girls and 64 boys from 7.9 to 9.7 years of age. After controlling for bone age, body mass, body height, and calcium intake, lean mass was the most important predictor of bone size and/or mineral in both genders (p \ 0.05), while habitual weight-bearing PA positively influenced BMC in boys (p \ 0.05). The effect of muscle in bone was not determined by PA and fitness score did not explain bone variability. Femoral neck was the bone site more closely associated with mechanical loading factors; boys with a PA ( 608 counts/min/day (*105 min/day of moderate and vigorous intensity) showed 13-20% more BMC than those with less physical activity, and girls with a lean mass (19 kg showed 12-19% more BMC than those with less lean mass. These findings suggest that lean mass was the most important predictor of bone size and/or mineralization in both genders, while habitual weight- bearing PA appears to positively impact on bone mineral in prepubertal boys and that both lean mass and PA need to be considered in physical education curricula and other health-enhancing programs.

O objectivo do presente estudo foi avaliar a natureza das alterações na capacidade de produção mecânica do complexo músculo-tendinoso, na fase de impulsão da transposição da barreira, induzidas pela aplicação de um protocolo de fadiga específico à prova de 400 metros barreiras. Sete barreiristas de elite nacional (idade: 24.43 ± 5.68 anos; altura: 1.82 ± 0.06 m; massa: 71.79 ± 5.84 Kg; melhor marca 400mB: 51.55 ± 1.72 s) participaram neste estudo. A acção de transposição da barreira foi filmada com uma câmara de alta velocidade (Redlake PCI1000), que permitiu o cálculo das coordenadas bidimensionais das articulações do membro inferior. Para estimar as alterações de comprimento dos complexos músculo-tendinosos durante a fase de impulsão da transposição da barreira foram utilizadas as equações de regressão adaptadas de Jacobs et al. (14). Uma plataforma de forças tridimensional foi instalada na pista, e as forças de reacção ao apoio (Fz, Fy e Fx) foram registadas a uma frequência de 1000 Hz e sincronizadas com o registo de vídeo. Estes procedimentos foram repetidos antes e após a aplicação do protocolo de fadiga. As diferenças entre condições foram testadas por T-Test para amostras emparelhadas. Os principais resultados mostraram que em condições de fadiga existe um aumento significativo da perda de velocidade horizontal do Centro de Gravidade (CG) (p